Arrangement for the automatic drawing in of the chain stitch in the whipping thread on sewing machines



Jan. 20, 1970 I L. M-J. BO'UC RAUT 3,490,403

ARRANGEMENT FOR THE AUTOMATIC DRAWING IN OF THE CHAIN STITCH IN THE WHIPPING THREAD ON SEWING MACHINES Filed Sept. 27, 1968 2 SheetsSheet 1 m/ we /u roR 40 0/5 Z 0 u /w ar- Jan. 20, 1970 L. M-J. BOUCZRAUT ARRANGEMENT FOR THE AUTOMATIC DRAWING IN OF THE STITCH IN Filed Sept. 27, 1968 3,490,403 CHAIN THE WHIPPING THREAD ON SEWING MACHINES 2 Sheets-Sheet 2 400/5 1700C R r United States Patent US. Cl. 112-252 6 Claims ABSTRACT OF THE DISCLOSURE In a sewing machine executing a whipping of the succession of pieces of fabric, the method and means for continuing the stitching of the whipping thread beyond the trailing edge of one piece of fabric, over the gap between said pieces of fabric and the next piece of fabric entering the machine and over the length of a few stitches in the leading position of said next piece after wh1ch a chain stitch in the whipping thread is cut inside said gap and the free end of the cut thread on the side nearest said next piece of fabric is folded back over the latter by a draught flowing over the whipping stitches already executed in said next piece of fabric, the whipping operation being then resumed over the folded back section of the chain stitch-forming whipping thread.

The present invention has for its object an arrangement for automatically drawing in chain stitches on machines operating on a commercial scale.

When sections of a woven or knitted fa-bric are assembled on a sewing machine such as a whipping or overcasting machine, the pieces of fabric obtained are interconnected in sequence by a stitch of a more or less com plex type, generally termed a chain stitch. When the chain stitch obtained by sewing is cut through so as to separate the piece of fabric which has already been sewn from the following piece of fabric which is then to be sewn, there appears a section of a chain stitch which must be stitched or fastened within the seam of the next piece of fabric to be sewn in order to prevent any un-' ravelling.

Such operations are generally performed by hand by the seamstress who, after she has executed a few stitches on the incoming piece of fabric to be sewn, stops the machine, cuts through the chain stitch, folds back the free end of the chain stitch underneath the needle of the sewing machine and finally starts the latter again. These operative steps are difiicult of and require much skill if it is desired to obtain a true uniformity for the successive pieces of fabric and all the more so since it is necessary to take into account the strain to which the seamstress is subjected; furthermore, this manner of operating leads to a considerable loss of time.

It has been proposed, it is true, to execute such tucking or drawing in steps for a chain stitch through the agency of a mechanical means, however, the latter has been hitherto constituted by a shiftable sucker arm adapted to engage the chain stitch and to transfer it to a point where it is ultimately inserted underneath the seam. Such mechanical means lead to an objectionable intricacy of the sewing system.

The present invention has for its object an arrangement for drawing in chain stitches, said arrangement being of a remarkable simplicity ascribable to the fact that it includes no mechanical part for the folding of the free end of the chain stitch, so that no intricate mechanism is any longer required. Such an arrangement allows the operator to execute the drawing in of the chain stitch within a time as short as that required in the case of a particularly skilled and efiicient seamstress. The machine is furthermore free from the strain arising in the case of human operation while the resulting work is much more uniform and the incorporation of the arrangement according to the invention provides a considerable economy in time and consequently leads to a much lower expenditure.

According to the invention, the automatic drawing in of the chain stitch is obtained after execution of a few stitches on the incoming piece of fabric and after cut ting through of the chain stitch by the folding of the released end of the chain stitch through the agency of a draught in a direction parallel with the seam, said draught extending over the few stitches already formed, after which the sewing is resumed.

The accompanying drawings illustrate by way of a nonlimiting example an embodiment of the invention with a view to furthering the understanding of said invention.

In said drawings:

FIGS. 1 and 2 show diagrammatically respectively from above and in side elevational view a machine equipped with an improved arrangement according to the invention.

FIGS. 3, 4 and 5 are fragmentary diagrammatic views illustrating the different stages of the drawing in of the chain stitch.

FIG. 6 is a wiring diagram of the electric circuits controlling the drawing in of the chain stitch.

In the embodiment illustrated, the sewing machine includes a belt conveyor 17 carrying above the work carrying table 1 of the sewing machine the pieces of fabric to be whipped. In FIG. 1, the two superposed'pieces of fabric, such for instance as knitted wear, which have just been whipped are shown at 4, while the two next incoming pieces of fabric are illustrated at 5.

The chain stitch is shown at 8, 8a between the two compound pieces of fabric 4 and 5. The sewing machine which is of any suitable type is illustrated in a diagrammatic manner as including a work-carrying table 1, a mechanism 2 with the needle 3, the usual presser foot 7 underneath which the incoming pieces of fabric 5 are engaged and a cutter 12, these different parts being associated and operating in a conventional manner wellknown in the art, so as to sew a Whipped thread along the fabric, while a section of the latter progresses underneath the needle. However, when the two successive pieces of fabric have passed beyond the needle, there appears a free strand between the trailing edge of the two front assembled pieces of fabric 4 and the leading edge of the next incoming pieces of fabric 5. The usual mechanical parts of the sewing machine adapted to form the loops constituting the stitches have not been illustrated since they do not form part of the invention and their description is therefore unnecessary.

According to the invention, the machine includes furthermore means for producing at the desired moment a draught extending in parallelism with the sewing line, said means being constituted in the example illustrated by a nozzle 14 blowing air in a direction facing the direction of progression F of the conveyor belt and by a second or sucking nozzle 16 connected with a low pressure system which has not been illustrated. It should be remarked that it is possible to resort in modified embodiments only to a blowing nozzle 14 or only to a sucking nozzle 16. There are also provided photo-elec tric means 11, 18 controlling respectively relays R1 and R2 providing therethrough operation at normal or at reduced speed as also the automatic stoppage of the machine as soon as it has executed a few stitches on the pieces of fabric 5 to be whipped, following which the cutter 12 is released so as to cut through the chain stitch.

When the complex piece of fabri 5 has sufliciently progressed for the execution of a few stitches therein, the following operations are started by an electric circuit system illustrated diagrammatically in FIG. 6 and described hereinafter in further detail.

FIG. 3 shows the piece of fabric 5 in a position such that the formed chain stitch 8, 8a extends underneath the cutter 12 just ahead of the suction nozzle 16. For this position, the piece of fabric 5 lies across the beam illuminating the photo-cell 11 controlling through the relay R1, the progression of the conveyor belt at a low speed; said operation at a low speed allows the piece of fabric 5 to stop in an accurate position under the action of the relay R2 controlled by the photo-cell 18. In fact, the piece of fabric 5 progresses across the beam of light illuminating said photo-cell 11 and this has for its result to stop the progression of the piece of fabric 5, to release the operation of the cutter 12 which cuts through the chain stitch and to start operation of the sucking nozzle 16, possibly with the blowing of air out of the nozzle 14. As apparent from inspection of FIG. 4, the corresponding section of the chain stitch 8a is then sucked in by the nozzle 16. At the end of the delay required for said suction exerted on the chain stitch, the machine starts again, so that the conveyor moves again in the direction of the arrow F (FIG. 5) whereby the end of the chain stitch 8a is engaged within the normal seam.

Turning now to FIG. 6, it is easy to understand the operation of the circuit system controlling automatically the starting and stoppage of the machine, the cutting through of the chain stitch, the drawing in of the chain stitch through blowing and/or sucking of air over it and the transient low speed progression of the conveyor belt.

The control circuits fed with conventional A.C. rectified at C include a circuit-breaker B and a. main switch M adapted to be actuated by the operator when starting the machine.

The sewing machine and conveyor belt are controlled through a clutch by a motor adapted to run at two operative speeds and to allow the machine to stop when the needle is in its uppermost position. Such a conventional so-called stop motor is in common use in the art.

The lever controlling the clutch energizing the motor is actuated by the electromagnet E1 fed with D.C.

When the circuit breaker B is not closed, the transistor T1 has its base negatively biased With reference to its emitter; consequently, current passes through the tram sistor and the collector is subjected to a voltage high enough for releasing the operation of the thyristors. The closing of the switch M then energizes the thyristor Th1 which closes the circuit of the electromagnet E1 controlling, as already'mentioned, the clutch energizing the motor of the sewing machine and the capacity C1 is simultaneously loaded. The clutch is actually controlled by a spring-urged lever subjected to the action of the said electromagnet E1.

The thyristor Th4 controls the cutter 12 while the thyristor Th5 controls the suction valve, which is not illustrated, in the suction pipe feeding the nozzle 16, said operation of the valve being ensured through the agency of the electromagnet E2.

Said thyristors Th4 and Th5 are in fact activated by pulses controlled by the capacities C4 and C5 inserted in their triggering circuits.

The thyristor Th4 is fed with the single alternations of a rectified current and consequently produces its own de-energization during the alternation following that corresponding to its ignition.

The delay in the suction is obtained through a further transistor T2 and a transistor of the single junction type UJT operating as a generator of pulses at an adjustable frequency. When the thyristor Th5 is activated, the base of the transistor T2 is negatively biased with reference to its emitter, so that it becomes conductive. The positive signal appearing on its collector biases the U] T transistor and allows the condenser C2 to be loaded. The duration of the loading of said condenser is adjustable, which allows an adjustment of the delay at the end of which the UJT transistor becomes conductive. When said conductivity has been obtained, the positive signal appearing on its negative base allows activation of the further transistor Th6 which discharges the capacity C3 and thereby extinguishes the thyristor Th5. As to the thyristor Th6, it is self-de-energized since it is fed by single phase alternations of the rectified current.

On the other hand, means are provided for operating the machine at a transiently reduced speed as provided by the spring-urged clutch-controlling lever actuated by the electromagnet Em, while the machine is stopped under the action of the electromagnet Ea. The photo-electric means 18 (FIGS. 1 and 2) actuate the relay R2 the opening of which de-energizes the relay Ra and thereby leads to the opening of the switch Ral and to the closing the switch Ra2, whereby the conveyor carrying the piece of fabric 5 is stopped. The thyristor Th2 stops the machine operating at its normal speed while the thyristor Th3 controls the relay the auxiliary switch a of which is adapted to stop. the machine when operating at a reduced speed.

The operation of the machine thus designed is as follows:

When a piece of fabric extends across the beam illuminating the photo-cell 11, the relay R1 closes and energizes the thyristor Th3, so as to discharge the condenser Cl and to extinguish the thyristor Th1. The clutchcontrolling lever is returned into its idle position by its spring and simultaneously closes the miniature switch m1. This provides for the energization of the relay Ra since R2 and A are inoperative. The switch Ral ensures operation of the clutch when the machine is running at a reduced speed.

When the beam illuminating the photocell 18 is cut off in its turn, the relay R1 opens and the relay Ra controlling the auxiliary switches Ral and Ra2 drops as soon as the switch S synchronized with the position of the machine needle opens. The auxiliary switch Ra2 opens then and the machine stops with its needle in its uppermost position. The machine is now ready to start again at normal high speed.

When it is desired to stop the machine during operation, it is sufiicient to close the circuit-breaker B so as to lock the transistor T1 and to prevent thereby any undesired starting of the operative cycle.

On the other hand, said circuit-breaker controls activation of the thyristors Th2 and Th3.

The thyristor Th2 switches oif the thyristor Th1 and consequently the clutch-controlling electromagnet E1 while the thyristor Th3 controls the relay A of which the auxiliary switch a stops the machine operating at a low speed. A short delay provided by a capacity and resistance circuit allows a transient energization of the thyristor Th3 during a period leading the machine to a complete stop.

What I claim is:

1. A method for automatically drawing in a chain stitch between successive pieces of fabric to be whipped as they progress through a sewing machine, said method consisting in continuing the execution of the whipping chain stitches between two successive pieces of fabric and over a short distance on the second piece, cutting the chain stitches between said two successive pieces of fabric, producing a stream of air over the whipping seam produced in a direction parallel with but opposed to the direction of progression of the pieces of fabric'to fold the cut chain stitch over whipped chain stitches in the second piece of fabric and resuming the whipping along the line defined by the folded chain stitches.

2. In a sewing machine adapted to whip a succession of pieces of fabric, an arrangement for automatically tucking in a whipping chain stitch between two successive pieces of fabric, said arrangement including a photoelectric system facing the whipping area and controlled by the entrance into said area of the leading edge of the second of said successive pieces of fabric, means controlled by said photo-electric system and adapted to transiently stop the operation of the sewing machine after execution of a few whipping stitches on said second piece of fabric and to cut through the chain stitch between said two successive pieces of fabric, means producing a stream of air over the whipping stitches executed between the pieces of fabric, said stream flowing over the cut end of the chain stitch nearest the second piece of fabric in opposite parallelism with the direction of progression of the pieces of fabric and further means causing the machine to resume operation after said stream of air has folded back said cut end over the last-mentioned whipping stitches.

3. An arrangement as claimed in claim 2, wherein the means producing a stream of air include a suction nozzle lying over the location of the leading edge of the second of the successive pieces of fabric as it enters the whipping area.

4. An arrangement as claimed in claim 2, wherein the means producing a stream of air include a suction nozzle lying over the location of the leading edge of the second of the successive pieces of fabric as it enters the whipping area, said last-mentioned means including furthermore means delaying the production of said stream of air over a predetermined short period.

5. An arrangement as claimed in claim 2, wherein the means producing a stream of air include a suction nozzle lying over the location of the leading edge of the second of the successive pieces of fabric as it enters the whipping area, said last-mentioned means including furthermore means delaying the production of said stream of air over a predetermined short period, and a circuit constituted by a transistor controlled simultaneously with the production of the stream of air, a further transistor of the single junction type adapted to generate pulses, means whereby said pulses cut off the stream of air and an adjustable rectified current circuit defining the frequency of said pulses.

6. In an arrangement as claimed in claim 2, a further photo-electric system facing the whipping area and controlled by the progression of the second piece of fabric beyond the point controlling the first-mentioned photoelectric system, and means controlled by the further photo-electric system and causing the sewing machine to run transiently at a reduced speed.

References Cited UNITED STATES PATENTS 2,849,974 9/1958 Tishler et a1. 112-252 XR 2,989,935 6/1961 Butler 112252 3,356,054 12/1967 Southwell et al 112-252 JAMES R. BOLER, Primary Examiner US. Cl. X.R. 112254 

